Don't had Amazon a default Date for Brink in their shop?
AFAIK they had...
Now they say:
http://www.amazon.com/Brink-Pc/dp/B002GDRPYI/ref=sr_1_3?ie=UTF8&qid=1294488714&sr=8-3
Confirmed or Fake?
Like Dysfunkshion said, Until SD releases something more on the release date. Any date found from places that are selling Brink are just arbitrary dates put there by the place thats selling it.
This thread shows you some on the arbitrary dates found http://www.gamesas.com/index.php?/topic/1153147-lets-see-how-many-different-release-dates-we-can-find-for-brink/page__p__16928321__hl__release__fromsearch__1#entry16928321